PHILADELPHIA — Giving up two home runs in the first inning — both with two strikes — was the first clue that Johan Santana was not his typical self last night.

“For the most part, he’s a guy who settles down,” Shane Victorino said after the Phillies smacked the Mets ace around for 10 runs over 3 2/3 innings in an 11-5 win at Citizens Bank Park to reclaim first place in the NL East. “He didn’t find a way to shut it down tonight.”

After Santana retired the Phillies in order in the second and third, he allowed them to erupt for nine runs in the fourth, capped by a bases-loaded walk to Jamie Moyer and a grand slam by Victorino, who didn’t expect the Phillies to dominate Santana to such a degree.

“As good as he is,” Victorino said, “you never think that.”

But the Phillies hit four homers off the southpaw and have now hit 10 off of him in his last three starts against them.

“He didn’t have his best fastball,” Phillies manager Charlie Manuel said. “It goes to show you a good pitcher can have an off night. His velocity was down from what we saw last year. Last year, he could hit 93-94 [mph] when wanted to. [Last night] he wasn’t there.”

Victorino agreed.

“He might not have been throwing as hard as he usually does,” Victorino said of Santana, who struck out just one.

Santana’s struggles seemed even more glaring in contrast to Phillies’ ace Roy Halladay’s performance on Saturday, when he dominated the Mets with a three-hit shutout.

Nevertheless, the Phillies refused to say they had Santana’s number.

“That was just one outing,” Victorino said. “You never take anything away from the guy.”

His manager agreed.

“He’ll bounce back,” Manuel said.

He wasn’t able to last night. Not after walking Carlos Ruiz to load the bases with two outs, then failing to retire the 47-year-old pitcher.

“I was just trying to get on base,” Moyer said of the at-bat, when Santana fell behind 2-0 and 3-1. “It shows that we’re all human.”